Background Being next-of-kin to someone with cancer requiring palliative care involves a complex life situation. Changes in roles and relationships might occur and the next-of-kin thereby try to adapt by being involved in the ill person's experiences and care even though they can feel unprepared for the care they are expected to provide. Therefore, the aim of this study was to develop a classic grounded theory of next-of-kin in palliative cancer care. Method Forty-two next-of-kin to persons with cancer in palliative phase or persons who had died from cancer were interviewed. Theoretical sampling was used during data collection. The data was analysed using classic Grounded Theory methodology to conceptualize patterns of human behaviour. Results Constructing stability emerged as the pattern of behaviour through which next-of-kin deal with their main concern; struggling with helplessness. This helplessness includes an involuntary waiting for the inevitable. The waiting causes sadness and frustration, which in turn increases the helplessness. The theory involves; Shielding, Acknowledging the reality, Going all in, Putting up boundaries, Asking for help, and Planning for the inescapable. These strategies can be used separately or simultaneously and they can also overlap each other. There are several conditions that may impact the theory Constructing stability, which strategies are used, and what the outcomes might be. Some conditions that emerged in this theory are time, personal finances, attitudes from extended family and friends and availability of healthcare resources. Conclusions The theory shows the complexities of being next-of-kin to someone receiving palliative care, while striving to construct stability. This theory can increase healthcare professionals' awareness of how next-of-kin struggle with helplessness and thus generates insight into how to support them in this struggle.